Ietsuki kobo (house yeast)

Ietsuki kobo (house yeast) refers to wild yeast that occurs naturally in a particular sake brewery. These yeasts are adapted to the brewery's environment and climate, and they can contribute a distinctive character to the flavor of the sake. However, compared with pure cultured yeast that has been isolated, house yeast generally produces more acid and does not produce enough alcohol. In many cases, the quality of its aroma and flavor is also lower. For this reason, skill and experience in brewing are important when house yeast is used. Because it can also bring out the individuality of a sake, one of its appeals is that, with careful technique, it can be used to create distinctive sake.